Option 1 is not cost effective as the rebuild parts come out more expensive than Option 2, to achieve three same standard. Option 3 is more expensive again, but perhaps the extra cost for some alloy calipers is worth it? From other posts, I gather that improvements to S2 front caliper are not required for normal use, however.

Hi Richard....no problem with standard S2 front brakes.... have you been in contact with http://www.biggred.co.uk they are very good ..on service and price...had a couple of pairs of calipers refurbed by them...and one pair of exchange......Steve

I have a pair of S2 calipers hat I have just cleaned ready for a rebuild. They didn’t need new pistons so the rebuild costs just the seals. And a cat of paint (I’m too cheap to get them plated).
However, I did split the calipers to clean them and that has left me with a dilemma. None of the seals kits contain the small square section seals between the caliper halves. And I have yet to source and purchase some. None of the normal sources can help and the few specialists I have contacted will not supply these seals.

I did split the calipers to clean them and that has left me with a dilemma. None of the seals kits contain the small square section seals between the caliper halves. And I have yet to source and purchase some. None of the normal sources can help and the few specialists I have contacted will not supply these seals.

XKS.com shows 162 in stock for 59 cents! but they will probably charge you another $20 to ship them..
I would try calling as they will sometimes put a small seal in an envelope, and four of these surely will fit.

I have a pair of S2 calipers hat I have just cleaned ready for a rebuild. They didn’t need new pistons so the rebuild costs just the seals. And a cat of paint (I’m too cheap to get them plated).
However, I did split the calipers to clean them and that has left me with a dilemma. None of the seals kits contain the small square section seals between the caliper halves. And I have yet to source and purchase some. None of the normal sources can help and the few specialists I have contacted will not supply these seals.

Following up my post, I note that brakeparts.co.uk have reconditioned front calipers for £65. At that cost, I don't think I will trouble myself with buying the parts for a rebuild. They have good prices for the disks and sundries also.